1. Field of the Invention
The present invention generally relates to information recording apparatuses and, more particularly, to an optical information recording apparatus provided with an optical amount control device for controlling a light-emitting power of a light source such as a semiconductor laser.
2. Description of the Related Art
In recent years, many information recording apparatuses, which record information on an optical recording medium such as a CD-R/RW, are used. For example, Japanese Laid-Open Patent Application No. 9-270128 discloses an information recording apparatus in which a light reflected by an optical disc is received by a photodetector during a recording of information, and a maximum value of an intensity of the reflected light from a pit part and an intensity of the reflected light after a reference time has passed from the tip of the pit part are extracted by a peak hold detection circuit and a sample hold circuit. The information recording apparatus detects a maximum value of intensities of lights reflected by a plurality of pits and intensities of sampled lights reflected by the pits for several frames in a practical recording area when starting information recording on the optical disc. The information recording apparatus obtains the maximum value of the intensities of the reflected lights and the intensity of the sample reflected light in accordance with the result of the detection. That is, the information recording apparatus detects the maximum intensity of the reflected lights and the intensity of the sampled reflected lights from the pit parts at the time of starting an information recording. The information recording apparatus compares the result of the detection with a reference value, and carries out a running optical power calibration (running OPC), which corrects a laser light in accordance with the result of the comparison.
Generally, when recording information on an optical disc, an optical disc apparatus generates a recording laser beam having a power higher than that used for reading.
In a case of an optical disc having a recording surface formed of an organic colorant recording film such as a recordable compact disc (CD-R), a semiconductor laser source emits a laser light alternately at a read power having P1 level and a write power having P2 level. The write power is set to be larger value than the read power (P2>P1). A pit is formed in the place where the laser light having the P2 level light-emitting power is irradiated on a recording surface, and the place where the laser light having the P1 level light-emitting power is irradiated corresponds to a space.
Moreover, P3 level higher than P2 level (P3>P2) may be set, and a recording power waveform may be generated according to three values of P1 level, P2 level and P3 level. A laser light having the P3 level record power is directed to a head of each pit so as to acuminate a leading edge of the pit.
The record power of the three values is also used when recording on a phase change type rewritable recording medium such as a rewritable compact disc (CD-RW). By repeatedly irradiating the P3 level light-emitting power laser light and the P1 level light-emitting power laser light at a high speed, the laser irradiated part on a recording surface is changed to an amorphous state. Then, the portion of the amorphous state is crystallized by continuously irradiating the P2 level light-emitting power laser light so that the crystallized portion represents information. The P2 level power and the P3 level power are determined, when writing information on an optical disc such as, for example, a CD-R/RW, by carrying out an optical power calibration of a recording laser power in a power calibration area (PCA) provided in an innermost portion of an optical disc before recording information.
However, the apparent laser power can change due to a change in a writing area of an optical disc, a temperature change with passage of time or a surface deflection and an eccentricity of an optical disc. Therefore, even if a recording starts at an optimal power determined by the PCA, it will be no longer optimal when it reaches a recording surface. Then, in the above-mentioned information recording apparatus, a laser power optimization method referred to as a running OPC method is carried out while recording information. In the running OPC method, the laser light reflected by the optical disc under a writing operation is sampled at a timing to emit a light at a high power to form a pit. Then, the sampled signal is monitored so as to be compared with a monitor signal similar to that when the OPC is carried out, and the power of the emitted laser is controlled to always be optimized so that the sampled signal and the monitored signal are at the same level.
However, in the conventional information recording apparatus which performs the above-mentioned running OPC, the record power at the time of actual recording on an optical disc changes from an optimum power due to external factors such as a change in a writing area of an optical disc, a temperature change with passage of time or a surface deflection and an eccentricity of an optical disc.
Additionally, since a modulation rate becomes extremely high when a recording speed is increased, a time during which the P2 level power is maintained is reduced, which requires a high-rate sampling circuit. However, generally, it is difficult to realize a high-rate sampling circuit, and even if it is realized, there will be a problem of a high cost. Then, if an inexpensive regular sampling circuit is used, there is a problem in which a recording power becomes inaccurate.